1. Field of the Invention
The present invention relates to a method of controlling quality of a printed image and an apparatus of controlling quality of a printed image by controlling the ink feed amount of each of a plurality of basic colors of a color printing press.
2. Related Art
There has been known a color printing press including a plurality of printing units each provided with a plurality of ink fountains that respectively contain printing inks of a plurality of basic colors that are different from each other (typically four colors including three colors of Cyan (C), Magenta (M), and Yellow (Y), as well as Black (Bk)), and a plurality of ink fountain keys each aligned with each of the ink fountains in the lengthwise direction so as to adjust ink feed amounts from the corresponding ink fountains, wherein the plurality of inks of basic colors whose ink feed amounts are adjusted for the corresponding ink fountains using the ink fountain keys are respectively fed to a plurality of printing plates that are provided corresponding to the plurality of ink fountains, and a plurality of images of basic colors respectively formed with the plurality of inks of basic colors that have been fed are sequentially printed on a subject to be printed, thereby obtaining a printed matter on which a color print image is printed.
In each printing unit described above, in the middle way of feeding the ink fed from the ink fountain to the printing plate, a group of a number of ink rollers is provided between the ink fountain and the printing plate.
Accordingly, there is a case in which a portion of the ink on the printed matter that is carried to the next printing unit moves to the ink fountain via the group of ink rollers of this printing unit.
While each ink generally includes a color component of the other ink as turbidity, the turbidity degree adversely changes to a large degree if two inks become mixed by the other ink moving to the ink fountain via the group of ink rollers during printing operation is made in the manner as described above, or the color that has been matched prior to printing adversely changes during the printing if a transfer ratio of one ink to be printed onto another ink (ink trapping ratio) changes.
Thus, there has already been proposed a technique of adjusting feed amounts of the inks during printing, taking into account the main color component and the turbidity color component of each ink (cf. Japanese Patent No. 3384769, for example).
An ink feed amount adjustment apparatus of Japanese Patent No. 3384769 measures a density value of a color on a printed matter that has been printed and adjusts a feed amount of an ink for each ink fountain so as to match the measured value with a desired density value, but does not take into account an adjustment of tints or hues (color differences) at all. Therefore, there is a case in which the tints or hues of the colors do not match, leaving much to be improved.